1. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 1/25 OVERVIEW OF SAFETY OF EUROPEAN FUSION POWER PLANT DESIGNS Annual Meeting on Nuclear Technology May 10 - 12, 2005 Nuremberg S.Ciattaglia, a L.Di Pace, W.Gulden, P.Sardain, b N.Taylor EFDA Close Support Unit, S&E Field, Garching Germany a ENEA Fusion Technologies, Frascati (Rome), Italy b Euratom/UKAEA Fusion Association, Culham Science Centre, Abingdon, UK

2. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 2/25 Outline Introduction Power Plant Conceptual Studies Safety analysis Environmental impact Radioactive wastes Achievements and open points Conclusions

3. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 3/25 Introduction From 1990 to 2000 a series of studies on safety, environmental and economic potential of fusion power potential to provide inherent safety and favourable environmental features, to address global climate change and gain public acceptance the cost of fusion electricity likely to be comparable with that from other environmentally responsible sources of electricity generation Further progress on experiments and R&D Substantial advances in the understanding of fusion plasma physics and in the development of more favourable plasma operating regimes, Progress in the development of materials and technology.

4. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 4/25 Introduction (2) PPCS (Power Plant Conceptual Studies) A comprehensive design study for commercial fusion power plants performed from mid 2001 to mid 2004, to serve as a better guide for the further evolution of the fusion development programme. Focussed on four (+1) power plant models, named PPCS A to PPCS D plus model AB, spanning a range from relatively near-term concepts, based on limited technology and plasma physics extrapolations, to a more advanced conception. They differ from one another in their size, fusion power and materials compositions, and these differences lead to differences in economic performance and in the details of safety and environmental impacts. The study was carried out with the help of a large number of experts from both the European fusion research community and its industrial partners.

5. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 5/25 Power Plant Conceptual Studies Objectives Demonstration of: Credibility of fusion power plant design Safety and environmental advantages of fusions power Economic viability of fusion power Set of requirements issued by industry and utilities Safety Operational aspects Economic aspects Economic safety and environmental analyses of these models were made

6. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 6/25 Schematic diagram of a tokamak fusion power plant Vac uu m Vessel

7. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 7/25 General layout

8. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 8/25 Key parameters 1500 MW e Fusion power is determined by efficiency, energy multiplication and current drive power Given the fusion power, plasma size mainly driven by divertor considerations

9. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 9/25 PPCS main elements All the models PPCS A to D are based on the tokamak concept as the main line of fusion development proceeding through JET, the world’s largest and most advanced operating machine, that is provides the basis for the plasma physics of ITER, under design finalisation. Two main elements: Blanket: Takes the energy of the energetic neutrons produced by the fusion process Neutrons absorbed by Li atoms to produce the fuel, tritium. Divertor for exhausting from the plasma chamber the fusion reaction products, mainly helium, and the associated heat power

10. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 10/25 Plants main features Model AModel BModel CModel D Fusion Power (GW)5.03.63.42.5 Blanket Gain1.181.391.17 Plant Efficiency0.310.360.440.6 Bootstrap Fraction0.450.430.630.76 P add (MW)24627011271 H&CD Efficiency0.6 0.7 DV Peak load (MW.m -2 )1510 5 Average neutron wall load2.22.02.22.4 Major Radius (m)9.558.67.56.1 Structural materialEurofer SiC/SiC CoolantWaterHeliumLiPb/HeliumLiPb BreederLiPbLi4SiO4LiPb TBR1.061.121.151.12 Structural materialCuCrZrW alloy SiC/SiC Armour materialW alloy CoolantWaterHelium LiPb Conversion CycleRankine Brayton Blanket DV

11. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 11/25 PPCS A and PPCS B Limited extrapolations in plasma physics performance compared to the design basis of ITER. Blankets based, respectively, on the “water-cooled lithium-lead” and the “helium- cooled pebble bed” concepts, using of a low-activation martensitic steel Divertors water-cooled divertor is an extrapolation of the ITER design and uses the same materials. helium-cooled divertor, operating at much higher temperature, requires the development of a tungsten alloy as structural material. Balance of plant model A based on PWR technology, which is fully qualified model B relies on the technology of helium cooling, the industrial development of which is starting now, in order to achieve a higher coolant temperature and a higher thermodynamic efficiency of the power conversion system

12. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 12/25 Model A Blanket Eurofer as structural material Water as coolant LiPb as breeder and neutron multiplier Outboard Module a 20˚ sector

13. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 13/25 Model A: Water-cooled Divertor High temperature Dv Low temperature Dv

14. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 14/25 Model B: He-cooled divertor ÜDivertor concept using helium as coolant and W as structural material ÜPeak load of 10 MW/m 2  necessity to optimize the heat exchange

15. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 15/25 PPCS Models C and D PPCS C and D are based on successively more advanced concepts in plasma configuration and in materials technology The objective is to achieve even higher operating temperatures and efficiencies Their technology stems, respectively, from a “dual-coolant” blanket concept (helium and lithium-lead coolants with steel structures and silicon carbide insulators) and a “self-cooled” blanket concept (lithium- lead coolant with a silicon carbide structure) In PPCS C the divertor is the same concept as for model B In PPCS D, the divertor is cooled with lithium-lead like the blanket. This allows the pumping power for the coolant to be minimised and the balance of plant to be simplified.

16. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 16/25 Model C : DC Blanket Scheme and main Features

17. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 17/25 EU Fusion Programme development needs ITER operation optimisation of low activation martensitic steels, development of tungsten alloys, and their testing in IFMIF, as armour material development of the more advanced materials envisaged in the PPCS development of blanket modules, to be tested in ITER development of divertor systems, capable of combining high heat flux tolerance and high temperature operation with sufficient lifetime in power plant conditions development and qualification of maintenance procedures by remote handling A DEMO power plant study has been lunched: a study to give guidance to the ITER-accompanying programme in plasma physics and technology

18. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 18/25 PPCS Safety analysis Aim Critical design review and relevant recommendations in order to Demonstrate that no design-basis accident and no internally generated accident will constitute a major hazard to the population outside the plant perimeter, e.g. requiring evacuation. Technique adopted Functional Failure Mode and Effects Analysis methodology to find out representative accident initiators a plant functional breakdown for the main systems. a FFMEA for each lower level function Two design-basis accidents and two beyond design basis accidents chosen and analysed in detailed for both Plant Model A and B

19. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 19/25 Safety analysis (2) Fusion Reactors will produce and contain radioactive materials that require careful management both during the operation (avoiding release in normal and accident conditions) and after decommissioning Main radioactive mobilisable inventories tritium in the in-vessel components and in the fuel cycle activated materials (dust originating from plasma-PFC interaction and corrosion products) Energies that can mobilise the above inventories during accident conditions decay heat electromagnetic energy chemical energy

20. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 20/25 SOURCE TERMS ASSESSMENT Normal working conditions Occupational dose PIE RAS BAS Thermodynamic transients Aerosols and H3 transport Containments Release from the plant DCF Overall Plant Analysis FMEA Radioactive waste Identification&classification Operational&Decomm waste Management On-site Recycling Final disosal Effluents PST EST DCF man*Sv/y dose/sequence to MEI frequency*dose Quantity and waste categories mSv/y General fusion safety analysis approach

21. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 21/25 PPCS safety analysis has benefited by the main conclusions of ITER safety analysis A comprehensive analysis of off-normal events and failures and combination of failures postulated to critically verify the design Source Terms: 1 Kg of tritium, 100 Kg of Be and W dust, 200 Kg of carbon dust ORE design target: < 0.5 person Sv/y Energies definition: magnetic, Protection/Mitigation systems definition (VV suppression tank, plasma shutdown, HVAC systems and capability of dust and tritium filtering Low decay heat at shutdown (360 ºC is PFC Tmax after 9hr from the plasma shutdown in case of LOCA in-vessel) Radioactive releases for all accident events below the project release guidelines (relevant doses ~ average annual natural background dose) Hypothetical events (all cooling systems or common cause failure damaging both vacuum vessel and cryostat): no evacuation, (<50 mSv). PFC Tmax ~ 650 ºC Safety analysis (4)

22. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 22/25 PPCS source terms Energies Decay heat Magnetic Activation ORE ? Sarebbe dadare di dati/assunzinifate Safety analysis (4)

23. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 23/25 Bounding accident sequences: complete unmitigated loss of cooling; no safety systems operation; conservative modelling. Temperature transients: example opposite - Model A after ten days. Maximum temperatures never approach structural degradation. Safety Analysis (5)

24. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 24/25 Bounding Temperature Accident Analysis Plant Model A Plant Model B TT TT

25. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 25/25 Specific activity of the mid-plane outboard first wall in four Plant Models Activation of tokamak structures and components

26. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 26/25 Safety Analysis (7) The most challenging scenario in terms of environmental release: “Loss of flow in one primary cooling loop with consequential in-vessel LOCA (Model B)”. Parametric analyses on the building leakage rate from Expansion Volume; Possibility to operate an Emergency Detritiation System to reduce environmental releases

27. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 27/25 Safety Analysis - Model B Loss of flow in one primary cooling loop with consequential in-vessel LOCA Reference building leakage rates Pressure inside VV, EV and PS Complete mobilisation of 10 kg of dust & 1 kg-T in the VV. Elevated environmental releases due to building leakage rate considered: (75%/d); 58 g-T, 109 g of W, 346 g of SS dusts. Parametric analyses Lower leakage rates: 1%, 10%; One cylindrical (H= 40.0 m; D= 46.0 m) concrete structure surrounding the EV, and having a thickness of 0.4 m, externally insulated. ECART results

28. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 28/25 Environmental Impact (1) Environmental source terms activated dust/ corrosion products tritium During normal operation negligible release (doses to the most exposed individual less than 1% of the natural background level), ALARA principle is applied for public and workers No emission of any of the greenhouse gases Conservatively assumed a mobilisation fraction of 100 % for the dust at the beginning of the accident sequence, 90% as HTO for T worst atmosphere conditions

29. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 29/25 Model B Ex-vessel LOCA + in-vessel LOCA (Containment response and environm. release) Total dust deposited Total dust airborne VV TCHS Dust in compart. T in the compart. Dust to the Env. 0.2 g 0.6 g 24 h For 7-day T release assume a linear release with the slope of 110 -8 kg/s. At 7 days T released = 5.4 g. T to the Env.

30. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 30/25 Model A ex-vessel LOCA results Pressure in TCWS vault, ST and DT TCWS ST DT 7-day ACP release <1 mg 7-day T release <3 mg ACP T

31. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 31/25 ÜBounding accident sequences for Models A and B: complete unmitigated loss of cooling; no safety systems operation; conservative modelling ÜMobilisation; transport within the plant; release and transport in environment; leading to: ÜConservatively calculated worst case doses to the MEI from worst case accident: ÜMODEL A: 1.2 mSv ÜMODEL B: 18.1 mSv ÜComparable with typical annual doses from natural background. ÜModel C and Model D worst case doses (analyses undergoing) expected to be lower (abbiamo dei risultati???) Environmental Impact (4)

32. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 32/25 Radioactive Wastes (1) ÜThe fusion radioactive waste is characterised by low heat generation density and low radiotoxicity compared to fission plant waste. Therefore recycling may be a viable option. ÜStoring the fusion radioactive materials for 50-100 years on the plant allows reduction of radioactivity level waste masses

33. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 33/25 For ALL the Models: ÜActivation falls rapidly: by a factor 10,000 after a hundred years ÜSignificant contribution to SRM and CRM from operational wastes ÜPotentiality to have no waste for permanent repository disposal ÜAlso tritiated +  activated wastes Wastes from model B Radioactive Wastes (2)

34. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 34/25 Radioactive Wastes (3)

35. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 35/25 Radioactive Wastes (4)

36. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 36/25 Radioactive Wastes (5) If no recycling is planned the amount of waste to be disposed after 100 years, is equal to the CRM+SRM amounts. They don’t require a deep geological repository. Suitability and capability analyses of the final waste repositories in a few EU countries to store the PPCS wastes are undergoing (Konrad and Gorleben in Germany, SFR and SFL 3-5 in Sweden, CSA in France, El Cabril and DGR in Spain). First results, limited to Model B and German conditions, indicate that the fusion reactor waste can be al disposed in Konrad. For a few ones, detritiation is necessary to meet the relevant limits

37. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 37/25 Achievements and open points Comprehensive safety analysis of PPCS has showed “No evacuation” criteria met with margin also in case of severe accidents (bounding accidents analysis and consequences) Intrinsic-passive safety features of nuclear fusion plants confirmed Lack of operating experience Reliability of prototypes PFCs erosion/deposition and transport in SOL Tritium retention and distribution in the tokamak Detritiation techniques ORE minimisation Quantity of operational waste Tritiated +  waste disposal

38. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 38/25 Conclusions (1) The four PPCS conceptual design for commercial fusion power plants differ in their dimensions, gross power, and power density All models meet the overall objectives of the PPCS (design, safety, economics) Plasma performance only marginally better than the design basis of ITER is sufficient for economic viability of fusion reactors Conceptual design of a helium-cooled divertor capable of tolerating a peak heat load of 10 MW/m 2 Definition of a maintenance concept capable of delivering high availability (75%) A first commercial fusion power plant - accessible by a “fast track” route of fusion development - will be economically acceptable, with major safety and environmental advantages

39. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 39/25 Conclusions (2) R&D is needed Materials Validation of Eurofer Use of ODS Temperature Welding Tungsten as structural material SiC/SiC He cooled divertor Integration and technology issues Attachment system and access to collectors

40. EFDA EUROPEAN FUSION DEVELOPMENT AGREEMENT EFDA CSU Garching S.Ciattaglia, page 40/25 Conclusions (3) ÜThe safety and environmental attractiveness of fusion power has been confirmed ÜBounding accident sequence analyses driven by internal events have revealed no surprise: “no evacuation criteria” is met Bounding accident sequence analyses driven by external events have to be completed Model B LOFA + in-vessel LOCA i provides the largest environmental source terms Wastes amount are significant There is the potentiality to have no need of permanent disposal waste after 100 years from shutdown if recycling is applied